(a) Field of the Invention
The present invention relates to a cellular system, and more particularly, to a method of controlling interference between adjacent cells in a cellular system.
(b) Description of the Related Art
A wireless communication system has a cell structure to provide an efficient system configuration. A cell is one of a plurality of areas divided from a large area to efficiently use frequencies. A system having a cell structure is referred to as a cellular system.
In the cellular system, a terminal located at a cell boundary is more subject to inter-cell interference. The inter-cell interference decreases the signal to interference and noise ratio (SINR) or signal to noise ratio (SNR) of the terminal, thus reducing the quality of service (QoS) and channel capacity and degrading the overall performance of the system.
To solve this, an interference alignment method that enhances the sum rate capacity of the system by aligning all interference signals in a particular area within a given has been proposed. According to the interference alignment method, interference signals are located within some of available degrees of freedom to enable interference-free communication within the remaining available degrees of freedom. However, in order to apply the interference alignment method, the total number of transmitting antennas must be equal to the total number of receiving antennas, and awareness of all channels is needed.
To solve this problem of the interference alignment method, a subspace interference alignment method has been proposed. According to the subspace interference alignment method, a multidimensional subspace is formed within an entire signal space, and interference signals between adjacent cells are aligned in the subspace. Even the same channel has a different channel gain according to a reference vector multiplied at the transmitting end forming the subspace. Therefore, if the channel gain becomes smaller, the channel capacity decreases, thus disabling efficient communication.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.